Woven stretch fabric having yarn crimp superimposed on filament crimp and method of making same



Nov. 18, 1969 G. w MANOCK 3,479,245

WOVEN STRETCH FABRIC HAVING YARN CRIMP SUPERIMPOSED ON FILAMENT CRIMP AND METHOD OF MAKING SAME Filed NOV. 25, 1964 FIG. 4

INVENTOR. GEOFFREY W. MANOCK ATTORNEY United States Patent 3,479,245 WOVEN STRETCH FABRIC HAVING YARN CRIMP SUPERIMPOSED 0N FILAMENT CRIMP AND METHOD OF MAKING SAME Geoffrey Windle Manock, Harrogate, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Nov. 25, 1964, Ser. No. 413,886 Claims priority, application Great Britain, Nov. 25, 1963, 46,440/ 63 Int. Cl. D03d 15/08, 17/00 US. Cl. 16177 Claims ABSTRACT OF THE DISCLOSURE A woven fabric having stretch properties in a given direction as a result of the presence of stretch yarns containing crimped thermoplastic filaments is treated to increase the stretch properties by tensioning the fabric in the other direction to increase the magnitude undulations in the stretch yarns, heat setting the increased undulations in the stretch yarns and releasing the tension whereby the yarn crimp is superimposed on the filament crimp in the stretch yarns.

This invention relates to woven fabrics with modified stretch characteristics.

Woven fabrics having stretch characteristics in the warp and/or weft are known. They may be produced by known methods comprising incorporating a yarn made from crimped filaments such as Ban-lon which is a stuffer box crimped yarn, Helanca which is a twist crimped yarn or other types of crimped yarn which have adequate crimp elongation, recovery and other properties, which will result in adequate stretch in fabric form, as hereinafter defined. Ban-Ion and Helanca are registered trademarks.

We have found that the stretch characteristics of woven fabrics which contain crimped filament yarns in the warp or weft can be modified and the stretch in that direction can be increased by a suitable treatment of the fabric.

In the specification of our United States Patent No. 3,316,610, a process is described for making stretch fabrics from synthetic fibres having a glass rubber transition temperature above 80 C. in which the woven fabric is stretched in one direction and allowed to relax in the other direction to cause crimp interchange followed by heat setting and then cooling the fabric in that condition. By this method using Terylene polyester fibre yarns, a one-way stretch of 10-30% can be obtained in staple fabric using a plain weave construction.

According to the present invention we provide a woven fabric having modified stretch characteristics due to yarn crimp in the fabric which has been fixed by a heat treatment in fabric form, the modified stretch characteristics being imparted in that direction i.e. in the warp or weft in which a crimped filament yarn has been incorporated and in which the yarns in the other direction preferably comprise a major proportion of thermoplastic fibres. The yarns with yarn crimp consist of thermoplastic filaments.

The crimped yarns for use in our fabrics are defined by their properties which impart at least stretch in a suitably woven fabric construction and which consist of filament yarns made from synthetic, linear polymers and which have been subjected to a crimping operation as a result of which the yarn having an initial denier of 40-250, develop crimp and bulk in woven fabric form during finishing operations. The yarns are capable of shrinking at least 15% to 50% or more, when placed in boiling water for 1 minute, and simultaneously developing bulk which is brought about by a curling up of the 3,479,245 Patented Nov. 18, 1969 filaments and which can subsequently be reversibly extended by applying a load of 0.04 g.p.d. By the term reversibly extended we mean that the yarn will retract between -100% on removal of the load. It should be appreciated that e.g. with nylon crimped yarns a scouring treatment of 60 C. is adequate, whereas with polyester crimped filament yarns a finishing treatment at a commercial boil is desirable. After our treatment in fabric form the crimped yarns have filament crimp and superimposed yarn crimp making them capable of being extended in excess of 20%.

We also provide a process of imparting modified stretch characteristics to a woven fabric which has a crimped filament yarn, as defined, in the warp or weft and which contains yarns preferably consisting of a major proportion of thermoplastic fibres in the other direction i.e. the weft or warp, comprising overfeeding or relaxing the woven fabric by 5 to 20% in that direction in which the crimped filament yarns are situated e.g. when entering a stenter, and stretching the fabric 4 to 15 in the other direction to bring about a yarn crimp exchange and heating the fabric for a time and at a temperature suitable for bringing about heat setting in the yarns. Suitable thermoplastic fibres are polyester fibres derived from terephthalic acid particularly polyethylene terephthalate fibres. The fabric is heated in the above configuration and allowed to cool in that configuration.

It should be noted that although most fabrics made from crimped yarns can be stretched and recovered from stretch, these stretch characteristics are 15% to 30% and depend on cloth construction and the type of stretch yarn which according to our process can be modified i.e. increased by at least 5%. If increased warp stretch is required then warp cn'mp should be increased and this can be done by stretching the fabric in width so that the weft crimp is reduced. This causes the warp crimp to increase by virtue of the crimp interchange properties of woven fabrics and the correct amount of overfeed will reduce the fabric in length, as the warp crimp develops.

The heating conditions during the stretching and relaxing step should be greater than those likely to be met during subsequent making-up or laundering treatments. We have found temperatures of to 220 for 30 to 60 secs. adequate for polyethylene terephthalate yarns. If increased weft stretches is needed, the fabric should be stretched in the warp direction and allowed to relax in the Weft direction, the new fabric configuration being fixed by heat and cooled in that configuration, before being removed from the processing zone, the fabric, of course, being a weft stretch fabric, with the defined crimped yarns in the weft.

The crimped yarns, before the treatment have filament crimp, i.e. the individual filaments in the yarn have e.g. sinusoidal or helical crimp, After the treatment which involves stretching the fabric in the transverse direction and heating, the undulations in the crimped yarn are increased by crimp interchange and set in that condition, thereby increasing yarn crimp, superimposed on the filament crimp.

The glass-rubber transition temperature of the synthetic thermoplastic fibres is determined by the dynamic extension method as described by P. R. Pinnock and I. M. Ward in Proc. Phys. 800., vol. 81, Part 2, No. 520, pages 260-275, 1963.

Suitable synthetic thermoplastic fibres are polyester fibres derived from terephthalic acid, particularly polyethylene terephthalate and other fibres derived from fibreforming polymers having a plastic memory and a transition temperature when wet, above 80 C. The term fibres includes staple fibres and filaments where the context so allows.

By the term stretch characteristics we means that the fabric can be elongated by at least in at least one direction i.e. in the warp or Weft direction and that this elongation under a load which must be below the elastic limit of the yarn crimp and not cause fibre rupture, is recoverable by at least 85%, i.e. when releasing the stretching force, the fabric will rapidly assume substantially its previous size and shape. A convenient minimum load is 2 kg. on a 2 inch strip of the fabric.

It should be noted that although most fabrics can be stretched and recovered from stretch the amount of stretch is only about 1 to 3% whereas our fabrics with the defined stretch characteristics can be elongated by at least preferably -40% after the treatment, but not before.

We have found that quite simple operations in finishing can increase yarn crimp and so give stretch characteristics. If increased warp stretch is required then warp crimp should be increased. This can be done by stretching the fabric in width so that weft crimp is removed. This causes the warp crimp to increase, by virtue of the crimp interchange properties of woven fabrics, and the correct amount of overfeed, the fabric will be reduced in length, as the warp crimp develops.

The heat setting can conveniently be carried out during stentering and should clearly be under conditions more severe than those likely to be met during subsequent making-up or laundering treatments and temperatures between 150 and 220 C. preferably e.g. 180200 C. for -60 secs. are considered adequate for our defined fibres. Under wet conditions and in steam, lower temperatures are adequate and temperatures between the glass-rubber transition temperature and 30 C. below the melting point of the fibres may be used.

If increased weft stretch is needed, the fabric should be stretched in the warp direction and allowed to relax in the weft direction, again the new fabric configuration being fixed by heat.

It has been found that the stretch characteristics vary with fabric construction and, for example, the effect is far greater in a loosely woven skirting than in a tightly woven rainwear fabric. If desired fabric setts can be modified so that the required finished construction is obtained.

If e.g. a pretreated fabric has little or no weft crimp, then we cannot stretch it in the weft direction and therefore we cannot crimp the yarns in the warp to give increased warp stretch or vice versa.

Very firm fabrics, e.g. rainwear fabrics are difficult to distort and therefore difiicult to convert into our fabrics with increased stretch characteristics.

The original stretch yarn, as defined, in the woven fabrics must be thermoplastic i.e. capable of being heat set after crimp inter-change has taken place and this deformation of the crimped yarns must be elastic so that when a load is applied of 2 kg. to a 2 inch strip of fabric, the fabric retracts again on removal of the load, due to the recovery from bending of the heat set yarns. It should be appreciated that the modified stretch properties of the fabric are due specifically to bending of the heat set yarns rather than elongation of the individual filaments either by uncoiling of crimp or actual elastic elongationas happens in known stretch fabrics composed of elongatable fibres such as rubber or of conventional crimped filament yarns.

Natural and non-thermoplastic fibres can also be used in the transverse direction, if inferior stretch properties can be tolerated.

The condition for the heat fixation of the yarns in the fabric when tensioned in one direction, will depend on the polymer from which the thermoplastic yarns are made. The temperature conditions must be chosen depending on the heat resistance of any fibres which may be blended with the fibres responsible for the stretch characteristics and the weight of the fabric to allow sufficient heat penetration. The other consideration is that the treatment tem- 4 perature should be in excess of that likely to be encountered in subsequent processing, use and wear.

For practical purposes the tensions required can be determined sufiiciently accurately by measuring the extension under loads which of course must be less than those which would ruin the fabric by breaking individual yarns. Extensions of 4-15 in one direction and allowing the fabric to relax in the transverse direction in which the thermoplastic heat settable yarns are by about 520%, are suitable for our fabrics.

Such fabrics after the treatment should have stretch characteristics of at least 20% and may have up to 50% stretch in the warp or weft when tested under a 2 kg. load for a 2 inch strip of fabric.

Lubrication of the yarns in the fabric is of importance. The tension required to produce a crimp interchange is lower if inter-fibre and inter-yarn friction is low. Textile lubricants containing silicones are preferred.

When crimp interchange takes place the slightly undulating parallel yarns in one direction of the fabric are pulled substantially straight, and at the same time the parallel yarns in the other direction are thereby pulled farther apart and the undulating path over and under the substantially straight yarns in the other direction is very much enhanced. It will be appreciated that for this crimp interchange to be possible the following requirements in fabric construction will have to be met:

(a) The spacing between the yarns in both directions should be such that the yarns lie in an undulating path due to the weave pattern at substantially right angles to each other.

(b) The spacing between the yarns should be such as to allow movement of the yarns in the transverse direction when the other set of yarns is pulled into straight lines under high tension.

(c) The spacing should not be too large between the yarns but appreciable undulation should be present to cause a substantial movement of the yarns in the other direction when one set of yarns is pulled straight.

(d) To assist movement between the yarns a lubricant may be provided on the surface of the yarns.

(e) The undulated yarns should contain a major proportion of fibres or filaments which during the heat treatment in the tensioned condition, can be heat set in that position under conditions such that this setting becomes practically irreversible during any subsequent processing or during wear.

Regarding (e) we have found that synthetic fibres having a glass rubber transition temperature below C. do not show any particular merit when used in the fabrics of our invention because the imparted setting is not permanent and is removed by subsequent heat treatments at temperatures even below the setting temperature when wet. Such synthetic filaments and fibres comprise the polyamides and isotactic polypropylene. On the other hand polyester fibres derived from terephthalic acid particularly polyethylene terephthal-ate fibres or copolyester fibres containing up to 10% of a second component, as well as polyacrylonitrile, fibres and fibres containing at least 80% polyacrylonitrile are suitable, since the stretch characteristics imparted during our process are not substantially affected by subsequent heat treatment at least at temperatures up to 80 C. i.e. below the glass-rubber transition temperature. No substantial distortion of the fabric during any subsequent heat treatment at temperatures above the treatment temperature should be allowed to take place.

From the foregoing it will be noted that the treatment to be effective our fabrics will have a characteristic appearance when examining the threads in the fabric preferably using a low degree of optical magnification. The yarns or threads in one direction will be substantially straight and show a crimp elongation or undulation of less than 3% under a load of 0.5 g.p.d. whereas the yarns which are causing the stretch characteristics in the fabric will show a crimp elongation of at least and up to 50% under the same load. The undulations which are illustrated in the drawing, take a substantially sinusoidal path, the angle of straight lines between the apieces of the undulations or crimps are preferably less than 90 of angle. In addition these crimped yarns will be composed from crimped filaments.

If our process is carried out on a continuous and commercial scale on a pin stenter and it is desire to impart e.g. increased warp stretch characteristics to the fabric, the stenter is adjusted to give a high weft tension and overfeed is increased until waviness along the selvage of the suitable fabric along the selvage is noticed. The overfeed is then reduced until the waviness just disappears. In a suitable fabric, crimp interchange will take place, provided the weft tension is sufficient i.e. that the weft yarns come to lie in a single plane in substantially parallel straight lines, whereas before this weft tensioning, the weft yarns lay in undulating substantially parallel path.

It is also possible, instead, to increase weft stretch in the fabric by applying warp tension and weft relaxation. If a pin or clip stenter is used the fabric should be stretched to the full desired extent before it is pinned or clipped. If this is not done the pins or clips will prevent warp extension. It is desirable to increase the grip of the delivery rollers.

When the desired tension has been applied to bring about the crimp interchange, the fabric is heat set in that condition and cooled, before allowing any relaxation. Instead of a stenter, cylinder setting machines can be used in which the fabric is held on cylinders rotating at progressively faster speeds, while it is pressed e.g. by pressure belts against the cylinders. Such machines are commercially available. One type is known as the Bates Cylinder Machine; it requires some modifications, by including the provision of tensioning bars at the feed end. In this case setting occurs on the cylinders which are heated to an appropriate temperature in order to bring about heating of the fabric to a temperature throughout of up to 200 C. preferably 180 C. depending on a given speed and heat transfer properties of the fabric.

In the case of fibres which have a rubber transition temperature when wet above 80 C., such as polyethylene terephthalate fibres we have surprisingly found that fabrics containing a major proportion of such fibres can be heat set e.g. to a first temperature as high as up to 30 C. below the melting point of the fibre, followed by our treatment at a lower second temperature, i.e. above the glass rubber transition temperature and at least 60 C. below the melting point, cooled, preferably to room temperature and then if desired heated a third time at a temperature lower than the second temperature but without applying any overall tensions in the stretch direction of the fabric, treated according to our invention.

This is of considerable practical importance since such a woven fabric can be heat setand stabilised against creasing at say 180 C., then treated according to our invention including heating for a second time at say 180 C., for 30 secs., to impart stretch properties to the fabric and cooling to below the glass rubber transition temperature, and when made up in a garment form e.g. trousers, a pleat may be inserted e.g. on a Hoffman press at say 135 C. for 1 minute without overall distortion of the fabric, thus resulting in a garment with a durable pleat, stretch characteristics in one direction and stabilised against shrinkage.

We, therefore, also provide a process for increasing stretch characteristics in one direction in a woven fabric containing crimped filaments made from a polyester at least in the direction in which it is desired to impart stretch characteristics comprising heat setting the fabric at a temperature 30 C. above the glass rubber transition temperature and at least 30 C. below the melting temperature of the polyester, stretching the fabric in one direction and allowing the fabric to relax in the other direction and which preferably contain a major proportion of polyester fibres or filaments to bring about crimp interchange and so that the yarns in the direction of tensioning come to lie substantially in a single plane along substantially straight parallel lines, during said heating of the fabric in that condition at a temperature above the glass rubber temperature and 30 C. below the melting temperature, cooling the fabric in that condition and if desired subjecting the fabric to a subsequent third heating at a temperature above the rubber transition temperature and if desired below the said second temperature without, however, applying any overall distortion to the fabric for the purpose of, for example, ironing or pleating but excluding stretching in the direction in which stretch characteristics have been imparted to the fabric.

The attached drawings illustrate a preferred embodiment of our invention in which FIGURE 1 is a diagrammatic isometric view of an untreated fabric on a greatly enlarged scale.

FIGURE 2 is an isometric diagrammatic view of the fabric of FIGURE 1 as it appears during or after the heat treatment.

FIGURE 3 is a sectional end view of the fabric of FIGURE 1 and FIGURE 4 is a sectional end view of the fabric of FIGURE 2.

FIGURE 5 is a diagrammatic side view of a cylinder setting machine, on a much reduced scale.

Referring to FIGURE 1 it will be seen that the yarns 1, 2 and 3 are interwoven with the stretch yarns 5, 6, 7 and 8. It will be seen that the yarns 1, 2 and 3 are slightly displaced through interaction with the yarn 5 (in the warp) and as can 'be seen by reference to FIGURE 3, where an additional yarn 4. is shown. When such a fabric is overfed onto a stenter in the warp direction and then stretched in the weft direction the weft yarns are straightened along virtually straight lines as can be seen by reference to FIGURE 2, whereas the yarns in the warp direction are displaced by crimp interchange, the undulations having been taken out from the weft yarns and increased in the warp direction in the yarns 5 6, 7, 8 and 9. FIGURE 4 which is a section through the fabric of FIGURE 2 along yarn 5 illustrates more clearly the greater crimp imparted to the yarn 5 and also that the yarns 1, 2, 3 and 4 in the warp direction now lie virtually in one plane.

Referring to FIGURE 5 a suitably woven fabric is unwound from a cloth beam 10 and taken oven an adjustable tensioning device comprising quadrangular beams 11, 12, 13, 14 and 15, in which the two beams 12 and 13 can be pivoted around axis 16 by a hand wheel 17. From beam 15 the cloth is taken up by feed rolls 18 and 19 followed by expander roll 20 for spreading the cloth before it is taken up by the heated cylinders 21 and 22, against which the cloth is pressed under higher pressure from driven transport rolls 23 and 24. Additional rolls 25, 26, 2'7 and 28 are covered with two sets of aprons 29 and 30 which help to press the cloth against cylinders 21 and 22. Delivery roll 31 feeds the cloth into a cooling zone 33 where the fabric may be suitably cooled with a blower using air at ambient temperature, before it is taken up by winding roll 32 to be wound up as cloth roll 34.

The following examples illustrate but do not limit our invention.

EXAMPLE 1 A number of fabrics with Terylene (registered trademark) polyethylene terephthalate filament Helanca (registered trademark) false twist yarn 2 ply 75 denier in the warp with 67/33 Terylene polyethylene terephthalate/viscose yarn in the weft, 3 denier 2 inch fibres, woven in twill and in bedford cord constructions had 24 to 25% stretch in the wrap when measured with a 2 kg. load on a 2" wide strip. The fabrics were stentered at 180 C. for 30 secs. with overfeed in the warp and very high weft tension, during which treatment they extended in width and contracted 6% in length. After this treatment the fabrics had 29-32% stretch and their recovery properties were unimpaired at 95%, the improvement in stretch properties being obtained by the increased crimp in the warp direction. Details of these fabrics before and after treatment are given in Table I.

TABLE I.-INCREASE IN STRETCH OF HELANCA STRETCH FABRICS Stretch as received Stretch after treatment No. of yarns Percent Percent per inch, Cotton count Percent nonrecoverable Percent nom'ecoverable No. warp/weft Denier of warp weft Weave ext. 2 kg. extension ext. 2 kg. extension 1 117 x 53 2/75/16 2/22 Calvalry twill. 24 3 31 3 2 117 x 48 2/75/16 2/22 do 4 32 5 3 117 x 70 2/75/16 2/22 Bedford cord. 24 3 29 3 4 117 x 64 2/75/16 2/22 2/2 twill. 25 4 29 2 EXAMPLE 2 5. A process according to claim 4 in which the fabric Treatment Before After Percent warp stretch in a 2 wide strip under load of 2 k 25 32 Percent recovery from stretch 95 95 It will be seen that the warp stretch in this fabric has been increased from 25 to 32% without thereby impairing the good recovery properties.

This fabric was made up into ladies trousers giving a very satisfactory performance during wear.

What we claim is:

1. A woven stretch fabric formed of two groups of interwoven yarns and having modified stretch characteristics in the direction of the yarns of one of said groups, said one group including thermoplastic filament yarns exhibiting stretch characteristics due to filament crimp and having additional stretch characteristics due to yarn crimp superimposed on the filament crimp, said yarn crimp being in the form of heat-set undulations corresponding to the spacing between the yarns of the other group, the yarns of said other group being substantially free of yarn crimp and being formed predominantly of thermoplastic fibres, the total stretch characteristics of said fabric resulting in part from the ability of said crimped filaments to elongate and in part from the ability of said heat-set undulations to bend.

2. A woven fabric as in claim 1 in which the thermoplastic fibres are polyester fibres.

3. A woven fabric as in claim 1 in the thermoplastic fibres are derived from terephthalic acid.

4. A process of imparting modified stretch characteristics to a woven fabric which has a crimped filament yarn in one direction and which contains yarns consisting of a major proportion of thermoplastic fibres in is heated and then allowed to cool in that configuration.

6. A process according to claim 4 in which the heating conditions during stretching and relaxing are greater than those to be met during subsequent normal use.

7. A process according to claim 4 in which the temperature during the heat treatment is to 220 C.

8. A process according to claim 4 in which heating is carried out for a time of 30 to 60 seconds.

9. A process for increasing the stretch characteristics in one direction in a woven fabric having stretch characteristics in said one direction resulting from the presence of crimped polyester filaments extending in at least said one direction, the yarns extending in the other direction being formed predominantly of polyester, said process comprising: heat setting the fabric at a temperature between about 30 C. above the glass-rubber transition temperature and at least 30 C. below the melting temperature of the polyester; tensioning the fabric in said other direction and allowing the fabric to relax in said one direction so that the tensioned yarns come to lie substantially in a single plane along substantially parallel lines and so as to increase the undulations in the yarns extending in said one direction; heating the fabric in that condition at a temperature above the glass-rubber transition temperature and 30 C. below the melting temperature of the polyester to set the increased undulations; and cooling the fabric before releasing the tension.

10. A process as in claim 9 including the steps of subjecting the cooled fabric to a third heating at a temperature above the glass-rubber transition temperature and below the temperature at which the tensioned fabric was heated.

References Cited UNITED STATES PATENTS 2,903,021 9/1959 Holden et al 139-425 ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner U.S. Cl. X.R. 

